Z01 HD 001123-12 LCE and Z01 HD 001124-12 LCE are companion projects that together investigate auditory communication in primates. The overall goal of these studies is to provide a comprehensive understanding of primate auditory communication in terms of development, neural mechanisms, endocrine factors, and social context. Two non-human primates, the squirrel monkey and common marmoset, are the main subjects of study, with additional data collected from other species where appropriate. Prior work in this project has shown that production of sounds that are the functional and acoustic equivalents of cry sounds in human infants are mediated by limbic cortex located along the anterior midline of the frontal lobe of the cerebral cortex, and that single neural elements in the auditory cortex (superior temporal gyrus) are particularly responsive to subtle differences in the acoustic structure of species-specific vocalizations, suggesting an important role in mediating individual differences (vocal signatures). Studies of endocrine mechanisms have shown that endogenous prolactin levels correlate with carrying time in infant retrieval tests, and that reducing prolactin by administering bromocryptine (a dopamine agonist) disrupts infant retrieval. New findings are (a) prolactin assayed from blood and urine samples (in squirrel monkeys) are correlated, with the noninvasive urine collection preferred due to increased compatability with ongoing behavioral observations. Based on analysis of data from 3 social groups, we concluded that urinary prolactin is postively associated with physical contact with infants and with the intensity of caregiving towards infants. Urinary cortisol is positively associated with level of social disruption brought about by the presence of older infants and juveniles, who spend a large portion of their daily time budget engaged in social play.